1. Technical Field
The present disclosure relates to a method for measuring a position, a non-transitory recording medium storing a position measurement program, and a radio apparatus for measuring a current position in indoor space, underground space, a place surrounded by tall buildings, and the like where Global Positioning System (GPS) signals are difficult to detect.
2. Description of the Related Art
Currently, a position measurement system adopting a GPS is used. The position measurement system is a system that receives signals from a plurality of GPS satellites in outer space with a GPS receiver and that identifies the current position of the GPS receiver on the basis of the received signals. If the GPS receiver is covered from above, it is difficult for the GPS receiver to receive signals. Therefore, it is difficult for the GPS receiver to measure the current position thereof using signals from the GPS satellites in a place where the GPS signals are difficult to detect, such as indoor space or underground space. In addition, even in outdoor environments, if there is an obstacle near the GPS receiver, such as a tall building, the GPS receiver might not be able to measure the current position thereof correctly, because the GPS receiver might hide behind the obstacle or receive an incorrect GPS signal reflected from the obstacle.
Furthermore, position measurement systems in the related art adopt an indoor GPS, such as an indoor messaging system (IMES), or Wi-Fi (registered trademark) routers. Such position measurement systems are described in, for example, Japanese Unexamined Patent Application Publication No. 2007-278756 and Japanese Unexamined Patent Application Publication No. 2010-159980. Since smartphones are now widely used, Wi-Fi routers are installed in indoor space or underground space so that a communication function of the smartphones can be used in the indoor space or the underground space. Each smartphone is capable of estimating distances between a Wi-Fi receiver incorporated thereinto and the plurality of Wi-Fi routers and determining the current position thereof using information regarding the distances between the Wi-Fi receiver and the plurality of Wi-Fi routers.